Unconventional valley-dependent optical selection rules and landau level mixing in bilayer graphene
Unconventional valley-dependent optical selection rules and landau level mixing in bilayer graphene
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DOI：
10.1038/s41467-020-16844-y
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发表时间：
2020-06
影响因子：
16.6
通讯作者：
L. Ju;Lei Wang;Xiao Li;S. Moon;M. Ozerov;Zhengguang Lu;T. Taniguchi;Kenji Watanabe;E. Mueller;Fan Zhang;D. Smirnov;F. Rana;P. McEuen
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作者：
L. Ju;Lei Wang;Xiao Li;S. Moon;M. Ozerov;Zhengguang Lu;T. Taniguchi;Kenji Watanabe;E. Mueller;Fan Zhang;D. Smirnov;F. Rana;P. McEuen
选择定则在确定原子、分子和半导体的基本光学性质方面具有重要意义。它们提供了对系统的对称性和相关电子状态的性质的一般见解。磁场中的二维电子气是一个模型系统，其中朗道能级（LL）之间的光学跃迁由与LL指数N相关联的简单选择规则描述。在这里，我们研究了高品质的双层石墨烯的光致发光层间的光跃迁的光电流光谱测量。我们观察到了谷依赖的光学跃迁，违反了传统的选择规则Δ| N| = ± 1。此外，我们可以通过调整双层石墨烯带隙来调整相对振子强度。我们的研究结果为可调谐半导体系统中磁场、能带结构和多体相互作用之间的相互作用提供了新的见解，并且实验技术可以推广到研究其他纳米和量子材料的破缺态和低能磁光性质。
Selection rules are of vital importance in determining the basic optical properties of atoms, molecules and semiconductors. They provide general insights into the symmetry of the system and the nature of relevant electronic states. A two-dimensional electron gas in a magnetic field is a model system where optical transitions between Landau levels (LLs) are described by simple selection rules associated with the LL indexN. Here we examine the inter-LL optical transitions of high-quality bilayer graphene by photocurrent spectroscopy measurement. We observed valley-dependent optical transitions that violate the conventional selection rules Δ|N| = ± 1. Moreover, we can tune the relative oscillator strength by tuning the bilayer graphene bandgap. Our findings provide insights into the interplay between magnetic field, band structure and many-body interactions in tunable semiconductor systems, and the experimental technique can be generalized to study symmetry-broken states and low energy magneto-optical properties of other nano and quantum materials.